Surgical conduit leak testing

ABSTRACT

Systems, devices, and methods for leak testing surgical conduit grafts or valved conduits such as aortic-valved conduits with a pressurized gas such as air. Air is non-destructive and especially useful for leak testing conduits that have coatings or sealants that may be functionally impacted when exposed to fluids such as water or saline. Open ends of the conduit are clamped and sealed, and a pressurized gas introduced into an inner lumen thereof. A change in mass flow rate is measured to quantify the leakage. One end of a tubular conduit may be clamped to a fixed manifold, and the opposite end to a manifold slidably mounted to accommodate any conduit elongation when pressurized. The clamping and sealing structure may be pneumatic and/or mechanical, and complementary contoured clamp members may be used to seal a scalloped external sealing ring of an aortic conduit.

RELATED APPLICATIONS

This application claims the benefit of U.S. Patent Application No.62/131,134, filed Mar. 10, 2015, the entire disclosure which isincorporated by reference herein.

FIELD OF THE INVENTION

The present disclosure relates to systems and methods for leak testingsurgical conduits, in particular, for leak testing valved conduits.

BACKGROUND OF THE INVENTION

Surgical valved conduits or grafts, including a prosthetic vascularconduit with an associated prosthetic valve to control flow of bloodthrough the conduit, may be used for various purposes including, forexample, the replacement of the aortic valve in conjunction with theascending aorta. The aorta is the largest blood vessel in the humanbody, carrying blood from the left ventricle of the heart throughout thebody. The ascending aorta is the first section of the aorta, which stemsfrom the left ventricle and extends to the aortic arch. The aortic valveis located at the root of the ascending aorta and controls the bloodflow by permitting blood to flow from the left ventricle into theascending aorta while preventing or restricting blood flow in theopposite direction.

In the so-called Bentall procedure, the combined pathologies ofascending aorta and aortic valve are replaced. There are a number ofcombined conduits and valves on the market. Prior bioprosthetic valvedconduits, as with bioprosthetic heart valves, are stored in a liquidpreserving or preservative solution, and thus the conduits are formed ofwoven polyester without a bioresorbable sealant. Although such conduitsare suitable in certain situations, and tend to seal relatively quicklyto the body from tissue ingrowth, too much blood can initially seepthrough their walls after implantation, which may be detrimental.Uncoated fabric such as polyethylene terephthalate (PET) has a highleakage rate, and thus the surgeon needs to pre-clot the graft withpatient's blood before use. Others have proposed using anon-bioresorbable sealant layer, such as silicone, for example, asdescribed in U.S. Patent Publication No. 2008/0147171 to Ashton, et al.,published Jun. 19, 2008, but such layered conduits tend to be relativelythick-walled and not very flexible, and so are not preferred. Forexample, BioValsalva™ porcine aortic-valved conduits (Vascutek,Renfrewshire, Scotland, UK) include either three layers with an innerwoven polyester, central elastomeric membrane, and outer ePTFE wrap, ortwo layers without the outer ePTFE layer. Nevertheless, such graftsstill produce unacceptable leaking.

Consequently, some surgeons prefer conduits or grafts in which poroustubular structures, such as woven polyester (e.g., DACRON® polyethyleneterephthalate (PET), Invista, Wichita, Kans.), are impregnated withbioresorbable materials such as gelatin, collagen, or albumin. Forinstance, Gelweave Valsalva™ Grafts (Vascutek, Renfrewshire, Scotland,UK) are gelatin sealed, aortic root grafts indicated for aortic rootreplacement. These conduits are not porous initially, and thus preventblood loss, but the sealant medium eventually degrades by hydrolysiswhen exposed to water after implantation and is replaced by naturaltissue ingrowth. Gelatin in the graft can also be treated in such a wayas to cause cross-linking between amine groups in the gelatin molecules,rendering the gelatin more resistant to hydrolysis.

Conduits or grafts sealed using bioresorbable materials that includebioprosthetic heart valves are not pre-assembled because the liquidsterilant in which tissue valves are stored will eventually wash thebioresorbable sealing medium (gelatin, collagen, albumin, etc.) out ofthe permeable conduit material. Because of the benefits of using sealedconduits or grafts and because of the positive attributes ofbioprosthetic heart valves, surgeons couple the two components togetherat the time of surgery, post-storage. Recently, so-called dry tissueheart valves have been developed, for example, described in U.S. Pat.No. 7,972,376 (Dove, et al.), in which bioprosthetic heart valves arepretreated with an aldehyde-capping agent prior to dehydration andsterilization. U.S. Patent Application Publication No. 2013/0325111 A1to Campbell, et al. discloses a valved conduit that utilizes such a drytissue valve connected within a tubular conduit sealed with abioresorbable material. The Campbell valved conduit may be stored dry ina pre-assembled state, thus eliminating the time-consuming process ofsecuring the two components together in the operating theater.

There remains a need for improved manufacturing techniques for valvedconduits that ensure long term viability and efficacy, in particular inensuring that the valved conduits will not leak excessively.

SUMMARY

The present application relates to systems and methods for leak testingconduit grafts or aortic-valved conduit devices that have coatings orsealants that may be functionally impacted when exposed to fluids suchas water or saline, or where exposure to such fluids is undesirable dueto the requirement for drying after testing.

Embodiments of the leak testing systems and methods disclosed herein areintended to be non-destructive so that each commercial product may betested if desired. Some embodiments of the test method avoid functionalimpact to the portion of the device exposed to the test medium, do notrequire preparation of solutions, and/or allow for faster testing andsimpler setup.

An exemplary embodiment of the leak testing system and method uses airas a medium to test for permeability/leakage of a part, for example, thegraft or aortic-valved conduit. The part is first plugged or clamped onboth ends to create a seal on each end. A variety of plug/clamp designsmay be used for this purpose. One end of the assembly is fluidlyconnected to an inlet port of a leak tester that is capable of mass-flowtesting. A lumen of the part is then pressurized with air, and a massair-flow test performed. This embodiment of the test method subjects thepart to air flow, and the measured change in air flow corresponds to anair leak rate from the part.

In an alternative embodiment of the test method, the part is internallypressurized with air for a first, typically short, period of time, thepressure is allowed to settle or equilibrate for a second, typicallybrief period of time, and the pressure decay is measured as air leaksfrom the part. A pressure decay threshold is identified to distinguish apassing from a failing part. For instance, the part may be internallypressurized to about 16 kPa (about 2.3 psi), and then monitored for aperiod of time. If the lumen pressure decays by more than 50% from thestarting pressure within a predetermined time period, such as 0.6seconds, then the part is deemed defective. Of course, these thresholdsare variable depending on the type of conduit, application, and startingpressure, among other variables.

Existing test methods are either destructive or require a drying periodfor the part. Since embodiments of the test methods disclosed herein useair, they are non-destructive and require no post-test drying period.Therefore, embodiments of the test methods allow 100% inspection ofparts, and/or repeated testing of the same sample. Depending on theclamp design contacting the graft, some slight disruption of the gelatinor collagen may occur at the clamp interface. In some of these cases, aslightly longer graft may be specified for the in-process graft design,and this segment may be trimmed off after the leak inspection, leavingthe final desired graft length for the end product. With air, nosolution storage or mixing is required. The part may be pressurizedrelatively quickly, and no solution evacuation or clean-up is required.

A method of manufacturing a valved conduit is also disclosed, whichincludes first assembling a valved conduit including a bioprostheticvalve having bioprosthetic tissue coupled to a conduit sealed with abioresorbable medium. The method includes leak testing each valvedconduit using air, and sealing the conduits deemed acceptable in drypackaging. The bioprosthetic heart valve preferably includes prosthetictissue that has been treated such that the tissue may be stored dry forextended periods without degradation of functionality of the valve. Forexample, the tissue may be cross-linked using glutaraldehyde or otheraldehyde containing agents, treated with a capping agent, and dehydratedwith a glycerol solution. The bioprosthetic heart valve may haveseparate bovine pericardial leaflets or a whole porcine valve. Thesealed conduit includes a tubular matrix impregnated with abioresorbable medium such as gelatin or collagen. The heart valve may besewn to the end of the conduit or coupled thereto with a snap-fitconnection to limit handling of the two treated components and provide ahemostatic seal with minimal assembly complexity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary leak testing fixture havinga surgical conduit therein with one end adapted to freely slide along atrack;

FIG. 2 is a top plan view of the leak testing fixture with the surgicalconduit therein of FIG. 1;

FIGS. 3 and 4A/4B are side and opposite end elevational views,respectively, of the exemplary leak testing fixture;

FIG. 5 is a vertical cross-section along a midline of the exemplary leaktesting fixture, and FIG. 5A is enlarged view of the surgical conduittherein;

FIGS. 6 and 7 are perspective exploded and assembled views,respectively, of a manifold assembly for sealing both ends of a surgicalconduit and applying pressure within a lumen therein;

FIGS. 8A and 8B are horizontal cross-sections of the manifold assemblytaken along line 8-8 of FIG. 7 illustrating the leak testing fixturebefore and after introducing pressurized gas to clamp and seal both endsof the surgical conduit;

FIGS. 9A and 9B are top plan and vertical cross-sectional views of theleak testing fixture after pressurizing the interior of the surgicalconduit with gas, causing the left-hand portion of the manifold assemblyto be displaced to the left (in the illustrated orientation);

FIG. 10 is a top exploded plan view of an alternative leak testingfixture, a valved conduit, and complementary end clamps for sealing oneend of the valved conduit;

FIGS. 10A and 10B are partial cutaway views of an exemplary valvedconduit that may be leak tested by the systems described herein;

FIGS. 11 and 12 are perspective exploded and assembled views,respectively, of an alternative manifold assembly for the leak testingfixture of FIG. 10 for sealing both ends of the valved conduit andpressurizing a lumen therein;

FIGS. 13A and 13B are horizontal cross-sections of the alternativemanifold assembly taken along line 13-13 of FIG. 12 illustrating usingpressurized gas to clamp and seal both ends of the valved conduit andafter application of pressurized gas within the interior of the valvedconduit, causing the left-hand portion of the alternative manifoldassembly to be displaced to the left;

FIGS. 14A-14D are perspective and orthogonal views of a first end clampfor use in the alternative manifold assembly;

FIGS. 15A-15D are perspective and orthogonal views of a second end clampcomplementary to the first end clamp for use in the alternative manifoldassembly.

FIGS. 16A-16D are perspective and orthogonal views of an alternativefirst end clamp for use in the alternative manifold assembly; and

FIGS. 17A-17D are perspective and orthogonal views of an alternativesecond end clamp complementary to the alternative first end clamp foruse in the alternative manifold assembly.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The present application discloses several systems for leak testingsurgical conduits or grafts using a pressurized gas, such as air, as atesting fluid. In a preferred embodiment, pressurized air is the gas,although any gas that is non-destructive and non-reactive (inert) to theparticular conduit being tested may be used, for example, oxygen,nitrogen, helium, argon, carbon dioxide, hydrogen, hydrocarbons,hydrofluorocarbons, fluorocarbons, fluorochlorocarbons,hydrofluorochlorocarbons, and combinations thereof. As used herein, theterm “air” includes all suitable gas test fluids, except where contextindicates otherwise. The use of a gas instead of a liquid testing fluidcan preserve the surgical conduit, which may comprise porous tubularstructures such as woven polyester (e.g., DACRON® PET, Invista, Wichita,Kans.) impregnated with bioresorbable materials such as gelatin,collagen, and/or albumin. In contrast, leak testing with liquid testingfluids can destroy the efficacy of the bioresorbable material. However,embodiments of the disclosed test fixtures may be useful for leaktesting using pressurized fluids in general (i.e., including liquids andsupercritical fluids), and such usage is contemplated. For instance,testing of samples of conduits for experimental or validation purposesmay be done with the current systems using fluids such as saline. Apressurized “gas” is distinct from a pressurized “fluid” as a gas iscompressible, and in some embodiments, dry. The term “dry”, as usedherein, means that the gas may contain water vapor, but at aconcentration or relative humidity to permit non-destructive testingand/or to not require post-testing drying of the tested device. The term“dry” does not require that the gas be anhydrous, although anhydrousgases are within the scope of the term. The term “inert gas”, as usedherein, means that the gas is substantially non-reactive or does notappreciably damage the tested device. The term “inert” does not requirethat the gas be a group 18 or noble gas, although such gases are alsowithin the scope of the term.

The term “surgical conduit” refers to a typically tubular length ofmaterial that is used as an implant to at least partially replace thefunction of a native section of the vasculature or heart, such as theascending aorta. A conduit has a lumen for fluid flow. The testingmethods described herein are useful for all types of conduits or grafts,and thus the term is used generally to refer to straight grafts,bifurcated grafts, branched grafts, and the like. The terms “conduit”and “graft” are used interchangeably herein, with the understanding that“graft” means a graft that functions as a conduit. Those of skill in theart will understand that the test fixtures described herein may bemodified to accommodate different types, shapes, and sizes of conduits.

The leak testing systems and methods of the present application areparticularly well-suited to testing valved conduits. The term “valvedconduit” refers to a surgical conduit that is coupled with orincorporates a one-way valve. The test systems and methods areparticularly well-suited for leak testing conduit grafts such as aorticconduits, and in particular, for valved conduits such as aortic-valvedconduits, which include a prosthetic aortic valve on one end coupledwith a tubular section of conduit to replace the ascending aorta. Someembodiments of aortic valve conduits including side branches extendingfrom a tubular main body for coupling to the outwardly extendingcoronary arteries are also contemplated for leak testing as describedherein, for example, with the side branches plugged, tied off, orotherwise closed for the leak test. Advantageously, a dry, bioprostheticheart valve coupled with a conduit impregnated with a sealing agent maybe leak tested with air in a non-destructive manner, as will beexplained below.

Current standards (ISO 7198) for permeability/leakage testing of graftsin general suggest the use of water or buffered saline as the testfluid. These leak test methods, when used on grafts coated with sealantssuch as gelatin or collagen, are destructive in nature. Exposure of thepart to fluids such as saline or water initiates hydrolysis of thegelatin/collagen, which may compromise in vivo sealing propertiesthereof. A destructive method may be adequate for design verificationtesting, in which the tested parts are not intended to be re-used, butintroduces limitations, for example, where repeat testing on the samesample may be desired. An in-process manufacturing inspection should benon-destructive.

FIG. 1 is a perspective view and FIG. 2 a top plan view of an exemplaryleak testing fixture 20 having a surgical conduit 22 mounted thereinwith one end of the testing fixture permitted to freely slide along atrack 24. FIGS. 3 and 4A/4B are side and opposite end elevational views,respectively, of the exemplary leak testing fixture 20. The test fixture20 comprises a generally rectangular horizontal base 30 elongated alonga length axis relative to a width dimension. The linear track 24 extendsfrom near one long end to approximately a midpoint of the base 30 in theillustrated embodiment. The linear track 24 has other configurations inother embodiments, for example, depending on the relative dimensionsand/or configurations of the base and other components of the testingfixture. A manifold assembly 34 mounts on the base 30 with a first end36 fixed to the base and a second end 38 coupled to slide on the base inthe long direction along the track 24. For the sake of orientation, theright end of the test fixture 20 corresponds to the fixed first end 36,and the left end of the test fixture corresponds to the sliding secondend 38 in the drawings.

The first end 36 includes an upstanding bracket 40 fixed on the base 30and has a gas flow port (not shown in FIGS. 1 and 2) therethrough influid communication with an inlet fitting or test gas port 42 on anouter side and with a support shaft 44 on an inner side. The supportshaft 44 connects to and provides structural support for a firstmanifold 46 a. The second end 38 includes a carriage 48 having a lowerchannel (not numbered) adapted to closely fit over and slide on thelinear track 24. Those skilled in the art will understand that otherarrangements are possible, for example, with the channel and trackdisposed on the carriage and the base, respectively. An upstanding framemember 50 fixed on the carriage 48 provides structural support for asecond manifold 46 b. Specifically, an elongated shaft 51 seen in FIG. 3connects to and provides structural support for the second manifold 46b. In some embodiments, the bracket 40 is equipped to slidelongitudinally, either in addition to or instead of the frame member 50.In the description of the manifold components, the term “inner” refersto the longitudinal direction toward the other manifold, and the term“outer” refers to the direction away from the other manifold. In otherembodiments, the inlet fitting 42 has a different location, for example,extending from a side of the bracket 40, from the base 30, from thesupport shaft 44, or from the first manifold, or from any location thatis fluidly connectable with the lumen of the conduit or graftto-be-tested, as will become apparent below.

The first and second manifolds 46 a, 46 b have generally cylindricalprofiles with coincident horizontal axes. Those skilled in the art willunderstand that manifolds with axially symmetric profiles, for example,cylindrical, feature simplified fabrication and/or assembly; however,other profiles are useful in other contexts, and certain components canhave profiles different than other components in some embodiments, forexample, the mandrels, as discussed in greater detail below. The conduit22 is held at either end by the first and second manifolds 46 a, 46 b,as will be described below. The illustrated surgical conduit 22comprises a tubular structure with circumferential corrugations forkink-resistance and longitudinal and bending flexibility. In embodimentsin which the conduit has a different shape, for example, in which theends are axially offset and/or in which the ends are non-parallel, therelative positions of the first and second manifolds are adjusted toaccount for the shape of the conduit.

With reference now to the vertical cross-sections of FIGS. 5 and 5A, andthe exploded view of FIG. 6, details of components of the manifoldassembly 34 (assembled in FIG. 7) are shown. The first and secondmanifolds 46 a, 46 b are substantially similar and their components willbe given the same element numbers aside from a pair of mandrels 60, 62which are configured differently.

Both manifolds 46 a, 46 b include an exterior housing 64 having internalthreads 66, as seen in FIG. 6, that mate with external threads 68 ontubular caps 70. In other embodiments, at least a portion of theexterior housing is received within the tubular cap, while in otherembodiments, an inner face of the exterior housing butts against anouter face of the cap to provide a substantially fluid-tight seal.Furthermore, in other embodiments, the exterior housing 64 and tubularcap 70 are assembled using another type of fastener or coupling means,for example, any combination and/or multiple of a bayonet mount, bolt,pin, lock ring, quick-connect, latch, clip, clamp, magnet, wedge,threading, and the like. In some embodiments, the alternative fasteningsystem permits rapid assembly and disassembly of the manifolds, forexample, for ease of cleaning, servicing, and/or reconfiguration fortesting different types of devices. Some embodiments include a sealingmeans between the exterior housing and tubular cap, for example, agasket or O-ring. As best seen in FIG. 5A, the combination of theexterior housings 64 and tubular caps 70 define internal steppedcavities 72 that enclose pneumatic components for sealing both ends ofthe tubular conduit 22. In particular, relatively large pistons 74reciprocate axially within the cavities 72. As seen best in FIG. 6, eachpiston 74 includes a generally tubular main body 75 having a cylindricallumen 76 that extends at a constant diameter therethrough, and anenlarged ring-shaped central flange 78 with a peripheral groove thatreceives a primary O-ring 80. Two secondary O-rings 82 are also fittedwithin external grooves on the reduced diameter ends of the main body75. FIG. 5A shows that the primary O-ring 80 seals against a largerdiameter portion of the stepped cavity 72, while an outer one of thesecondary O-rings 82 seals against a smaller diameter portion thereof.An inner one of the secondary O-rings 82 seals against an inner lumen ofthe cap 70.

Still with reference to FIG. 5A, an inner end of the piston main body 75abuts against a rigid circular outer washer 90 a within the tubular cap70. On its other side, the outer washer 90 a abuts against a pair ofelastomeric clamping rings 92 which, in turn, contact a rigid circularinner washer 90 b. The assembly of the washers 90 a, 90 b andelastomeric clamping rings 92 is sandwiched between the piston main body75 and a radially-inwardly directed neck or lip 94 on the inner end ofthe cap 70. The reader will notice annular spaces 96 formed between thecentral flanges 78 of the pistons 74 and the outer end of the caps 70.These spaces 96 enable linear inward movement of the pistons 74 tocompress the elastomeric clamping rings 92, as will be explained below.It should be noted that although two clamping rings 92 are illustratedon both manifolds 46 a, 46 b other embodiments include a differentnumber of clamping rings on either or both of the manifolds 46 a, 46 bfor example a single clamping ring or greater than two. Furthermore,some embodiments independently omit either or both of the inner washerand outer washer on each manifold.

FIGS. 8A and 8B are horizontal cross-sections of the manifold assembly34 before and after introducing a pressurized fluid causes the manifolds46 a, 46 b to clamp and to seal to both ends of the surgical conduit 22.Here, the pressurized fluid is desirably a gas, such as air, thoughincompressible fluids, such as water, an organic liquid, or afluorocarbon, may also be used. A user loads the conduit 22 into themanifold assembly 34 by fitting the ends around respective mandrels 60,62, which are held in place by the respective shafts 44, 51. The outerends of the conduit 22 extend a short distance within or into the caps70, and at least as far as the inner one of the two elastomeric clampingrings 92. The shafts 44, 51 are secured with respect to the upstandingbracket 40 and upstanding frame member 50 (referring back to FIG. 3).Bolts 98 extend between the respective bracket 40 and upstanding framemember 50 to the corresponding exterior housings 64, which fix thehousings with respect to the shafts 44, 51 and mandrels 60, 62.Furthermore, a tubular bushing 100 closely surrounds each of the shafts44, 51 and, in turn, is closely surrounded by the pistons 74. Thebushings 100 center the pistons 74 around the shafts 44, 51 but permitlinear displacement thereof. Preferably, the bushings 100 are press fitwithin the lumen 76 of the pistons 74, and slide easily over the shafts44, 51. In other embodiments, the at least one of the bushings isintegrated with the respective piston or the shaft.

With reference still to FIGS. 8A and 8B, both of the exterior housings64 have flow channels 110 that extend from an exterior, for example, anouter face, thereof into communication with the respective internalstepped cavities 72. More particularly, each of the flow channels 110opens to the corresponding cavity 72 at a radially-oriented step 112(see FIG. 8B) that initially opposes the outer face of the centralflange 78 of the piston 74. An actuation fluid port 114, which is anelbow fitting in the illustrated embodiment, attaches to the outer faceof the housing 64 and provides a coupling point for attaching a hose(not shown) for delivering pressurized gas to the flow channel 110, aswell as for venting or releasing the actuation gas pressure. Otherembodiments include a separate port for venting pressure.

FIG. 8A shows the pistons 74 in their first or outer positions prior tointroduction of pressurized gas to the flow channels 110. The readerwill notice slight radial gaps between the elastomeric rings 92 and theexterior of each of the mandrels 60, 62 and surgical conduit 22 thereon.Again, the annular spaces 96 shown between the central flanges 78 of thepistons 74 and the outer end of the caps 70 enable or permit inwarddisplacement of the pistons.

The two mandrels 60, 62 preferably comprise identical main bodies eachhaving gradually stepped radii from an outer end to an inner end. Inembodiments in which at least one end of the conduits has differentand/or a different diameter, the respective mandrels are shapedaccordingly. With reference to FIG. 6, an outer cylindrical section 120of the mandrel has the largest radius, and is separated from a slightlysmaller middle cylindrical section 122 by a small inward step (notnumbered). Another small inward step leads to an inner section 124 thattapers down in size to its inner end 126. The surgical conduit 22 has adiameter that closely fits around the middle cylindrical section 122,abutting or contacting the small step at the beginning of the largestdiameter outer cylindrical section 120 in the illustrated embodiment(FIGS. 8A, 8B). Both mandrels 60, 62 have stepped-diameter axialthroughbores commencing at an inner bore 130 leading to a progressivelylarger outer bore (not numbered) that receives the respective shafts 44,51. A nut feature 132 or other such plug member, which is optionallythreaded to mate with complementary threading in the inner bore 130,closes off the throughbore in the second mandrel 62 such that there isno gas communication with a lumen 134 within the conduit 22. Otherembodiments do not include a plug so long as the manifold 46 b issubstantially sealed or leak-free. On the other hand, no such plugmember is provided for the first mandrel 60 such that its throughboreopens to the lumen 134 and provides an internal port at the inner end126 of the first mandrel for introducing pressurized gas therein.

FIG. 8B shows the pistons 74 displaced inwardly, as indicated by a pairof arrows superimposed on each piston, after pressurized gas isintroduced into both flow channels 110 through the actuation gas ports114. Although more than one flow channel could be provided, theaxi-symmetric nature of the central flange 78 of the pistons 74, as wellas the concentricity provided by the bushings 100 cause the pressurizedgas to be distributed annularly around the piston and to exert asubstantially even axial force thereto. As previously explained, theinner end of the piston main body 75 abuts against the circular outerwasher 90 a within the tubular cap 70. Inward displacement of thepistons 74 squeezes the elastomeric rings 92 between the rigid washers90 a, 90 b by virtue of the caps 70 being fixed with respect to theexterior housings 64. The elastomeric rings 92 are thus deformedradially inward as indicated in FIGS. 8A and 8B so as to contact andseal against both the mandrels 60, 62 and the surgical conduit 22. Thatis, the elastomeric rings 92 clamp and seal the surgical conduit 22against the rigid mandrels 60, 62, and in particular against the middlecylindrical sections 122 thereof. The gas pressure is calibrated suchthat the force of the pistons 74 is sufficient to cause the rings 92 toform an air tight seal against the exterior of the conduit 22, at itsends. Each piston 74 is independently actuatable and/or actuatabletogether. In some embodiments, the pistons 74 are actuated or displacedin the respective manifold by another method, for example, anycombination of pneumatic, hydraulic, electric, magnetic, or mechanicalactuation. Any pressurized gas introduced into the conduit lumen 134reaches the inside wall of the conduit 22 at least as far as the areasurrounding the tapered inner cylindrical section 124. At this point,the leak test fixture 20 is prepared for testing the conduit 22.

FIGS. 9A and 9B are top plan and vertical cross-sectional views of theleak testing fixture after introducing pressurized gas into the lumen134 of the surgical conduit 22. More specifically, a pressurized gas isprovided to the inlet fitting 42 that communicates with a hollow lumen140 through the support shaft 44. In the illustrated embodiment, theinlet fitting 42 is used to both pressurize and vent the test fixture.Other embodiments include a separate port for venting the test gas fromthe test fixture. As mentioned, an inner end of the shaft 44 engages thethroughbore in the first mandrel 60 such that the pressurized gascontinues into the lumen 134 of the surgical conduit 22. A small O-ring142 provides a seal between the exterior of the shaft 44 and thethroughbore in the first mandrel 60, and is optional in otherembodiments. Since the second mandrel 62 is sealed by nut or plug 132,and both ends of the conduit 22 are sealed, the pressurized gas canescape only through the wall of the conduit. The present testing systemmeasures any such leakage. The pressurized gas for leak testing isdesirably an inert gas such as air.

As indicated by the movement arrows in FIGS. 9A and 9B, pressurizing theconduit lumen 134 causes the left-hand or second end 38 of the manifoldassembly 34 to slide on the base 30 in the long direction along thetrack 24 as the conduit lengthens. Extension of the corrugated conduit22 permits this movement, and as a result the conduit contracts radiallysomewhat from its elongation, as shown by arrows in FIG. 9A. If thesecond end 38 of the manifold assembly 34 were restrained from sliding,the conduit 22 would tend to bend and possibly kink from the change inlength, which potentially causes additional leakage where folds or thelike expose or otherwise expand leaks, and/or masks leakage an otherwiseleaky portion of the conduit surface is covered or compressed by akinked or folded conduit surface. In some embodiments, the length of theconduit 22 does not appreciably change during the leak test. Asmentioned above, if disruption of the sealant, for example, gelatin orcollagen, on the sealed conduit 22 occurs at the clamp interface, aslightly longer graft may be specified, and the end segments may betrimmed off after the leak inspection, leaving the final desired graftlength for the end product.

A method of leak testing a conduit is a flow test, for example, a massair-flow test. In some embodiments of the flow test, the conduit is heldat a substantially constant gas pressure, and a flow rate is measured,for example, using a mass flow meter. The conduit is then graded—forexample, pass or fail, or with the measured flow rate—based on the flowrate. In one embodiment, the test or inlet fitting 42 of the testfixture 20 is fluidly connected, for example, via a hose or the conduit(not shown), to the port of an air or gas leak tester 150 (shownschematically in FIG. 9A) that is capable of mass-flow testing. Theconduit 22 is then pressurized with air or a test gas through the inlet42 to a substantially constant target pressure for a first or fill timeperiod, and a mass flow test performed for a second or test time periodat the target pressure. Finally, the lumen of the conduit isdepressurized or vented. This test method subjects the tested part toair flow, and the measured change in air flow corresponds to theair-leak rate through the test sample.

The target pressure depends on factors including the type of test gasused, the structural properties of the conduit, the nature of thesealant, and the like. In some embodiments, the target pressure isselected for accurate and reproducible leak test measurements. Forexample, at low pressures, minor differences in a physical orientationof a conduit could result in different measured leak rates, for example,from overlapping portions of the conduit blocking leak paths. On theother hand, a target pressure that is too high could damage the sealantlayer, creating new leak paths. Furthermore, the selected targetpressure is also depends on the properties of the test equipment. Forexample, in some embodiments, the mass flow meter both measures gas flowand regulates the gas pressure. Consequently, the target pressure isselected from a range of pressures that the mass flow meter is able tomaintain over the test time for a typical range of conduitsto-be-tested, for example, at least 3 sigma or at least 4 sigma, or atleast 5 sigma of the conduits. In some embodiments, the target pressureis from about 3.5 kPa (about 0.5 psi or about 25 mm Hg) to about 70 kPa(about 10 psi or about 520 mm Hg), or from about 7 kPa (about 1 psi orabout 50 mm Hg) to about 35 kPa (about 5 psi or about 150 mm Hg), orfrom about 14 kPa (about 2 psi or about 100 mm Hg) to about 28 kPa(about 4 psi or about 200 mm Hg). In some embodiments, the targetpressure includes a narrow range of pressures, for example, where themass flow meter controls the pressure in a discrete or quantized manner,for example, by opening and closing a valve controlling a source ofpressurized gas at a constant pressure that is higher than the targetpressure.

The fill time is selected to pressurize the conduit to the targetpressure rapidly, without causing any damage, for example, from suddenpressure changes. In some embodiments, a pressurization rate during thefill time is non-linear, for example, at a slower rate as the pressurein the conduit approaches the target pressure. For example, in someembodiments, the pressurization rate is sigmoidal, including three fillstages, with a slower initial fill rate, a faster main fill rate, and aslower final fill rate. Other embodiments include two fill stages, forexample, a faster initial fill rate, and a slower final fill rate. Insome embodiments, the fill time will depend on the leakiness of theconduit being tested. Embodiments of the fill time are from about0.1-500 s, from about 1-60 s, from about 2-30 s, or from about 5-15 s.

The test time is sufficiently long to obtain a stable, accurate, andreproducible flow rate, and as such, will depend on both thecharacteristics of the conduit to-be-tested, as well as of the flowmeter. Embodiments of the test time are from about 0.1-500 s, from about1-60 s, from about 2-30 s, or from about 5-15 s. The vent time isselected for rapid venting of the pressure without damaging the conduit,for example, from mechanical stress arising from sudden longitudinalcontraction of the conduit. Embodiments of the vent time are from about1-30 s, or about 5-10 s. In one embodiment, a target pressure of about16 kPa (about 2.32 psi or about 120 mm Hg), a fill time of about 10seconds, a test time of about 10 seconds, and a vent time of about 8seconds are used.

Another test method is a static test that includes mounting the testpart to the test fixture 20, as described above, pressurizing the partwith air or gas for a first time period (e.g., a short time), allowingthe pressure to settle for a second time period (e.g., a short time),and measuring the pressure decay as air leaks from the part for a thirdtime period. A pressure decay threshold is identified to distinguish apassing from a failing part. In one embodiment, a target pressure ofabout 16 kPa (about 2.32 psi, or about 120 mm Hg), a fill time of about10 seconds, a settle time of about 0.1 seconds, and test times ofbetween about 0.1-0.8 seconds are used.

After completion of the leak test, the pistons 74 are deactuated, forexample, by releasing fluid pressure at the actuation fluid ports 114.In the illustrated embodiment, gas in the annular space 96 returns thepiston 74 from the second position illustrated in FIG. 8B to the firstposition shown in FIG. 8A. Optionally, a reduced pressure, for example asource of vacuum, is fluidly connected to the actuation fluid port toretract the piston. Other embodiments include a component or mechanismfor returning the piston to the first position, for example, at leastone of spring, mechanical, pneumatic, hydraulic, electric, or magneticmechanism or actuator. After the release of the piston pressure, theelastomeric rings 92 relax back to their uncompressed states, therebyreleasing the ends of the conduit 22 therefrom, thereby permittingremoval of the ends of the graft 22 from the respective mandrels 62.

Some embodiments of the leak test system are at least partiallyautomated, for example, any combination of clamping the conduit,unclamping the conduit, leak testing the conduit, or recording theresults of a leak test.

Up to now the leak testing system 20 has been described in the contextof testing a straight tube conduit 22, for example, one formed of ahomogeneous graft material. As mentioned, other conduits may be testedwith certain modifications to the system facilitating the testing, forexample, for mounting the test part to the testing fixture. Forinstance, FIGS. 10-15 illustrate a modified system 220 for leak testinga valved conduit 222. Some aspects of the system 220 are common with theearlier-described system 20, and such features will be given the sameelement numbers albeit incremented by 200 (e.g., mandrel 60=mandrel260). Unless otherwise specified or apparent, alternative configurationsor arrangements discussed in conjunction to the leak testing fixture 20also apply to the leak testing fixture 220.

FIG. 10 is a top, partially exploded plan view of the modified leaktesting fixture 220, the valved conduit 222, and complementary endclamps 226, 228 for sealing each end of the valved conduit. FIGS. 11 and12 are perspective exploded and assembled views, respectively, of thealternative fixture 220.

The test fixture 220 comprises a generally rectangular horizontal base230 elongated along a length axis relative to a width dimension. Alinear track 224 extends from near one long end to approximately amidpoint of the base 230. A manifold assembly mounts on the base 230with a first end 236 fixed to the base and a second end 238 coupled toslide on the base in the long direction along the track 224.

The first end 236 of the manifold assembly includes an upstandingbracket 240 fixed on the base 230 and having a gas flow porttherethrough in communication with an inlet fitting 242 on an outerside, and with a support shaft 244 on an inner side. The support shaft244 connects to and provides structural support for a first manifold 246a. The second end 238 includes a carriage having a lower channel (notnumbered) adapted to closely fit over and slide on the linear track 224.An upstanding frame member 250 and shaft 251 fixed on the carriageprovides structural support for a second manifold 246 b. In FIG. 10, thevalved conduit 222 is shown exploded from between the two manifolds 246a, 246 b, and flanked by the complementary end clamps 226, 228. As willbe explained, the end clamps 226, 228 come together to seal around asewing flange 252 on one end of the conduit 222 within the secondmanifold 246 b, while the opposite end of the conduit extends over amandrel 260 and is sealed within the first manifold 246 a. In someembodiments, the positions of the first and second manifolds areinterchanged.

With reference now to FIGS. 10A and 10B, the valved conduit 222preferably includes a tubular graft portion 253 and a subassemblyincluding a one-way flow valve attached to a first end of the graftportion. The one-way flow valve permits fluid flow from one end of thetubular graft portion 253 to the other but prevents flow in the oppositedirection. In some embodiments, the one-way flow valve is a prostheticheart valve. In some embodiments, a valved conduit including a fullyassembled one-way flow valve subassembly is leak tested. In otherembodiments, it is advantageous and/or efficient to test just thosecomponents of the one-way flow valve subassembly that attach to thetubular graft portion 253, such as with sutures, so as to verify thevalved conduit does not leak around its exterior. Components such asvalve leaflets are generally internal to a surrounding supportstructure, and thus are not directly connected to the graft portion 253,and consequently, are not typically additional sources of leakage. Assuch, in some embodiments, some or all internal components of the flowvalve subassembly may be added after the leak test without affecting theintegrity of the conduit 222.

In the illustrated embodiment, the one-way flow valve comprises abioprosthetic heart valve having a sewing flange 252 surrounding aperipheral support structure 255 and a plurality of flexiblebioprosthetic tissue leaflets (not shown) attached to the supportstructure and extending inward to provide the air-flow occludingsurfaces. The support structure 255 may take a variety of forms, buttypically includes metallic or plastic rings with an axial component toprovide peripheral support for flexible leaflets. For instance, someembodiments of the valve have substantially the structure of acommercially available prosthetic heart valve, for example, aCarpentier-Edwards Magna® pericardial aortic bioprosthesis (EdwardsLifesciences, Irvine, Calif.). Alternatively, various other types offlow valves may be utilized to form the valved conduit 222, includingother bioprosthetic valves or mechanical valves. For example, someembodiments of the valve may have mechanical bi-leaflets, and thesupport structure 255 includes a ring with internal pivots to which theleaflets are pivotably mounted. A preferred valved conduit having abioprosthetic valve mounted therein is disclosed in International PatentPublication No. WO 2014/145811 A1 to Murad, filed Mar. 17, 2014, theentire contents of which are expressly incorporated herein by reference.

The illustrated conduit 222 is particularly suited for attachment withinthe aortic annulus and ascending aorta, and as such, closely matches theaortic root anatomy and includes three sections: a sinus section 257having axial corrugations or pleats, an aortic section 258 havingcircumferential corrugations or pleats, and a skirt section 259 (FIG.10B) that is used to couple the graft portion to the valve, or toexterior components thereof. The circumferentially corrugated sidewallof the aortic section 258 provides longitudinal flexibility and radialcompressibility while ensuring that the graft does not unduly radiallyexpand under the pressure of blood flowing therethrough. Thelongitudinal corrugations of the sinus section 257 are more radiallyexpandable than the circumferential pleats to allow expansion at thatlocation into the Valsalva sinuses adjacent to the aortic valve. Theconduit 222 desirably has an overall length of from a few centimeters toabout 10-15 centimeters. In the preferred embodiment, the conduit 222comprises a textile structure, such as a woven and/or non-woven PET(DACRON® PET, Invista, Wichita, Kans.), sealed with a bioresorbablemedium such as gelatin or collagen.

With respect to the enlarged view of FIG. 10B, the skirt section 259 isshown extending between the sewing flange 252 and the peripheral support255 of the valve, and wrapping underneath (on the left side, in FIG.10B) the sewing flange. The peripheral support 255 typically has one ormore fabric coverings, including an extended section 261 that wrapsunderneath the sewing flange 252 on the outside of the skirt section259, and is secured thereto with a peripheral line of stitches 262.Additional stitches may be provided between the various fabric sections,although stitches are preferably avoided in the tubular areas of theconduit 222 to reduce leakage through any holes formed thereby. Twocircumferential seams 263 (FIG. 10A) connect the sinus section 257 toboth of the aortic section 258 and skirt section 259. In otherembodiments, the skirt section is secured to the one-way valvesubassembly in a different way. As will be explained below, the leaktest fixture 220, and in particular the end clamps 226, 228, provide afluid-tight seal around the sewing flange 252 such that a pressurizedgas can only escape through the wall of the tubular conduit 222.

FIG. 11 illustrates the components of the modified manifold assemblyexploded for a better understanding of the differences between the twomanifolds 246 a, 246 b. The first manifold 246 a, which is on the endfixed with respect to the base 230 in the illustrated embodiment, housescomponents that seal around the end of the tubular aortic section 258 ofthe conduit 222. In this embodiment, the first manifold 246 a preferablyhas the same construction as the manifolds 46 a, 46 b described abovefor sealing the ends of the straight tubular graft 22. In particular, anouter housing 264 has internal threads that mate with external threadson a cap 270. The combination of the outer housing 264 and cap 270define an internal cavity within which is mounted a piston 274 having athroughbore that receives a tubular bushing 300 that slides on the shaft244 (FIG. 10). As explained above, the piston 274 contacts andcompresses a sandwiched assembly of inner and outer washers 290 a, 290 band elastomer rings 292. Finally, the aforementioned mandrel 260 mountsto an inner end of the shaft 244, as is shown in FIGS. 13A and 13B.

The second manifold 246 b also includes an outer housing 264 to which aninner cap 270 couples with threads. Within the cavity defined by thehousing 264 and cap 270, a piston 274 mounted to a tubular bushing 300is arranged to slide axially. Because the second end of the conduit 222has the one-way valve, and in particular the outward sewing flange 252,the piston 274 acts on a combination of the two end clamps 226, 228instead of flat washers or rings, as will be described in greater detailbelow. Some embodiments of the outer housing 264 and inner cap 270 ofthe second manifold 246 b include a fastener system or coupling meansthat is configured for rapid assembly and disassembly thereof, asdescribed above in conjunction with manifolds 46 a, 46 b, the utility ofwhich will become apparent.

Now with reference to FIGS. 13A and 13B, horizontal cross-sections ofthe alternative manifold assembly taken along line 13-13 of FIG. 12first illustrate introduction of pressurized gas to clamp and seal bothends of the valved conduit 222, and then introduction of a pressurizedgas for leak testing. Again, both the pressurized gas for clamping andpressurized gas for leak testing are preferably air. FIG. 13A showspressurized gas entering each of two inlet fittings 314 on bothmanifolds 246 a, 246 b. As in the earlier-described clampingconfiguration, the pressurized gas displaces the respective pistons 274inwardly, or towards the middle of the assembly. In the first manifold246 a, the piston 274 causes axial compression and the radially-inwardbulging of the two elastomeric rings 292, as discussed in detail above.This clamps the tubular end of the conduit 222 against the mandrel 260.In the second manifold 246 b, the piston 274 causes the two end clamps226, 228 to compress the resilient sewing flange 252 therebetween. Theouter of the two end clamps 228 has a solid or closed midsection orcenter, and thus closes off and seals the end of the conduit 222 havingthe partially or fully assembled one-way valve subassembly. Because bothends of the conduit 222 are sealed, the pressurized gas can only escapethrough the wall of the conduit.

FIG. 13B illustrates introduction of a pressurized gas within theinterior of the valved conduit 222. More particularly, the pressurizedgas will be introduced through the inlet fitting 242 shown in FIG. 10which is in fluid communication with an inner lumen 340 of the shaft244. The lumen 340 in turn leads to throughbore in the mandrel 260opening to an internal lumen 334 of the conduit 222. Pressurizing theinside of the conduit 222 in this manner causes the conduit 222 tolengthen as the pleats in the aortic section 258 unfold. Consequently,the movable second manifold 246 b slides to the left on the track 224,as indicated by the movement arrows in FIG. 13B, to accommodate thelengthened conduit 222. Once again, this linear displacement of one ofthe manifolds prevents the conduit 222 from bending, kinking, orotherwise distorting. Furthermore, the elongation of the conduit 222causes a slight contraction in the diameter of the aortic section 258.

The methods of testing for leaks in the valved conduit 222 are similarto those described above. That is, a mass air or gas flow test may beperformed which subjects the conduit 222 to air or gas flow, and themeasured change in air flow corresponds to an air leak rate from thetest sample. Alternatively, a static test in which the valved conduit222 may be pressurized with air for a short period of time, and then thepressure decay measured as air leaks from the conduit. It should benoted that clamping the sewing flange 252 between the end clamps 226,228 effectively isolates the central tubular portion of the valvedconduit 222 as well as the junction between the sinus section 257 andsewing flange 252 for leak testing. Consequently, the test concentrateson those portions of the conduit 222 that are most susceptible toleakage, the external portion of the valved conduit, rather than theportions that are less susceptible, for example, the seams or stitchinginternal to the one-way valve. When implanted, the sewing flange 252anchors one end of the valved conduit 222 to an anatomical location suchas the aortic annulus. Leakage between the flange 252 and surroundinganatomy is generally a consequence of a surgeon's skill rather than anyinherent leakage in the conduit itself. Thus, end clamps 226, 228 of theleak testing system effectively remove leakage between the sewing flange252 and tissue from the leakage measurement. On completion of the leaktest, the conduit is released from the fixture as described above.

FIGS. 14A-14D show the first end clamp 226, while FIGS. 15A-15D show thesecond end clamp 228 complementary to the first end clamp for use in thealternative manifold assembly. The first and second end clamps 226, 228have complementary contoured facing surfaces that generally conform tothe valved conduit sewing flange 252 and clamp the flange therebetweento provide a sufficient seal against leakage.

More particularly, the first or inner end clamp 226 of FIGS. 14A-14D hasa generally annular body 350 with a lumen 352 therethrough. Withreference to FIGS. 11 and 13A, the inner end clamp 226 fits closelyaround the tubular aortic section 258 of the valved conduit 222. Acontoured ledge 354 on the outer face of the clamp 226 contacts an innerside of the sewing flange 252 and mirrors its shape, for example, anundulating shape in the illustrated embodiment. More particularly, thesewing flange 252 desirably has a shape that matches the aortic annulus,with three peaks for the three commissures of the annulus intermediatethree valleys for the sinus regions. FIG. 14A illustrates three concavedepressions 356 sized and shaped to mate with the three peaks of thesewing flange 252, and three convex regions 358 sized and shaped to matewith the three valleys. Other embodiments of the sewing flange have adifferent profile, for example, with two peaks and two valleys forpatients with bicuspid aortic valves, and the outer face of the clamp226′ is complementary to the profile of the sewing flange.

The second end clamp 228 of FIGS. 15A-15D includes an annular body 360with an axially-oriented annular stub 362 projecting outward therefrom.A portion of the inner face of the annular body 360 includes a contouredsealing surface 364 that contacts an outer side of the sewing flange 252and mimics its undulating shape. In particular, alternating convex peaks366 and concave depressions 368 around the circumference of the sealingsurface 364 are sized and shaped to closely conform to the peaks andvalleys of the sewing flange 252.

The clamps 226, 228 do not require screws and nuts to connect the twopieces together and are relatively lightweight and user friendly. Inparticular, the clamps 226, 228 are placed around the valved conduit 222as depicted in FIG. 10 and rotationally oriented with respect to thesewing ring 252 using their matching undulating geometry. Alternatively,the clamps 226, 228 are rotationally oriented via alignment pins (notshown) that extend from one into dead-end holes in the other. Theassembly of the clamps 226, 228 around the valve end of the valvedconduit 222 is then inserted into cap 270 (FIG. 11) which is thenscrewed into outer housing 264 with the piston 274 and tubular bushing300 therein. The piston 274 applies some tension as cap 70 is engaged tohold the assembly in place. Again, the assembled components are seen insection in FIGS. 13A and 13B.

FIGS. 16A-16D and 17A-17D are perspective and orthogonal views ofembodiments of alternative first and second end clamps 226′, 228′,respectively. The first or inner end clamp 226′ shown in FIGS. 16A-16Dhas a generally annular body 370 with a cylindrical lumen 372therethrough. Much like the first embodiment of clamps 226, 228, andwith respect to FIGS. 11 and 13A, the inner end clamp 226′ fits closelyaround the tubular aortic section 258 of the valved conduit 222. Acontoured ledge 374 on the outer face of the clamp 226′ contacts aninner side of the sewing flange 252 and mirrors its shape, for example,an undulating shape in the illustrated embodiment. More particularly,the sewing flange 252 desirably has a shape that matches the aorticannulus, with three peaks for the three commissures of the annulusintermediate three valleys for the sinus regions. FIG. 16A illustratesthree depressions 376 sized and shaped to mate with the three peaks ofthe sewing flange 252, and three concave regions 378 sized and shaped tomate with the three valleys. Other embodiments of the sewing flange havea different profile, for example, with two peaks and two valleys forpatients with bicuspid aortic valves, and the outer face of the clamp226′ is complementary to the profile of the sewing flange. The end clamp226′ further includes a series of axial through-holes 379 in the annularbody 370 adjacent a peripheral edge thereof.

The second or outer end clamp 228′ shown in FIGS. 17A-17D includes anannular body 380 with an axially-oriented shaft stub 382 projectingoutward therefrom. A portion of the inner face of the annular body 380includes a contoured sealing surface 384 that contacts an outer side ofthe sewing flange 252 and mimics its undulating shape. In particular,alternating convex peaks 386 and concave depressions 388 around thecircumference of the sealing surface 384 are sized and shaped to closelyconform to the peaks and valleys of the sewing flange 252. The end clamp228′ also includes a series of axial through holes 390 in the annularbody 380 adjacent a peripheral edge thereof that align with thethrough-holes 379 in the first clamp 226′. Although not shown,complementary screws or bolts and nuts are inserted in the alignedthrough-holes 379, 390 to align and secure the two clamps 226′, 228′together.

As with the first-described clamps 226, 228, and with reference to FIG.13B, the assembly of the end clamps 226′, 228′ and sewing flange 252 issandwiched between the piston 274 and a radially-inwardly directed neck(not numbered) on the inner end of the cap 270. Introduction ofpressurized gas to the inlet fitting 314 on the second manifold 246 bcompresses the sewing flange 252 between the end clamps 226′, 228′.Providing the contoured ledge 374 and sealing surface 384 helps providean effective seal around the sewing flange 252, and avoids deforming theflange which might impact its functionality post-implant. The shaft stub382 is shown slightly within the lumen of the tubular bushing 300, whichhelps the center the clamping assembly.

The present application provides techniques that are particularly usefulfor testing implantable valves with sealed conduits, and in particularbioprosthetic heart valves that have been dried and do not need to bestored immersed in a preservative solution. The term “dried” or “dry”bioprosthetic heart valves refers in general to bioprosthetic heartvalve suitable for storage without immersion in a liquid or solution(e.g., a saluting including a preservative like glutaraldehyde), and inparticular to dry storage for extended periods without loss ordegradation of functionality of the bioprosthetic valve. There are anumber of proposed methods for manufacturing dry bioprosthetic heartvalves, and for manufacturing dry tissue suitable therefor, and thepresent application provides non-destructive methods of testing valvedconduits having such dry valves that are processed by any of thesemethods. The removal of a percentage of water from the valve, and inparticular, the tissue, and replacement thereof with glycerol andethanol allows the device to be stored “dry” (i.e., glycerolized). Avalved conduit including a dry bioprosthetic valve is ready forimplantation without the need for a clinical rinse in saline, therebyshortening implant time. In some embodiments, “dry” bioprosthetic tissuehas less than about 70% water content. In terms of practicalrehydration, functional valves have at least about 70% water content.Among the important distinctions of “dry” valves (or tissue therein),however, is that they may be stored dry for extended periods (sometimesyears) without degradation of functionality of the valves.

If air or another inert gas is used as the pressurizing medium for thetesting, every single valved conduit can be rapidly tested during themanufacturing process. That is, the leak test is non-destructive, andwith the use of the illustrated system, can be accomplished in arelatively short time. A “dry” bioprosthetic valve coupled to a sealedconduit can be tested for leaks and, if it passes, can be immediatelydry packaged for shipping and delivery. Or, preferably, the exteriorcomponents of the valve can be tested within the conduit, and then theremaining valve components assembled prior to sealing into sterilepackaging. Consequently, embodiments of the disclosed system provide100% quality control.

While the systems, devices, and methods have been described withreference to particular embodiments, it will be understood that variouschanges and additional variations may be made and equivalents may besubstituted for elements thereof without departing from the scope of thedisclosure. In addition, many modifications may be made to adapt aparticular situation or device to the teachings herein without departingfrom the essential scope thereof. Therefore, it is intended that thedisclosure is not be limited to the particular embodiments disclosedherein, but includes all embodiments falling within the scope of theappended claims.

What is claimed is:
 1. A surgical conduit leak testing system,comprising: a manifold assembly mounted on a common support baseincluding a pair of spaced apart manifolds having structure for clampingand sealing onto opposite ends of a surgical conduit, wherein a firstmanifold is fixed with respect to the support base and a second manifoldis mounted on the support base for movement toward and away from thefirst manifold, and wherein one of the manifolds has gas flow passagesbetween an external fitting and an internal port that opens to aninterior of the surgical conduit when clamped thereon; a gas deliveryhose connected to the external fitting; a gas pressure controller towhich the gas delivery hose attaches and which has a fitting forconnection to a source of pressurized gas, the controller having sensorsfor measuring the pressure in the gas delivery hose and an output forthe measured pressure; wherein the surgical conduit comprises a valvedconduit having a tubular graft portion and a one-way valve attached to asecond end of the graft portion, the one way valve permitting flow fromthe second end to the first end but preventing flow in the oppositedirection; wherein the valved conduit includes a resilient sealing ringadjacent the one-way valve which extends radially outward from the graftportion, and wherein the structure for clamping and sealing includes apair of rigid clamps sized and shaped to axially compress the sealingring; and wherein the structure for clamping and sealing includes flowchannels through both manifolds from external fittings, each manifoldhaving an internal piston arranged to be displaced toward the surgicalconduit when pressurized gas is introduced to the respective flowchannels, the piston in the manifold that receives the second end of thegraft portion configured to contact one of the rigid clamps and compressit against the other, and the structure on the manifold that receivesthe first end of the graft portion includes an elastomeric ring that iscompressed by piston displacement and positioned to expand inward andclamp and seal the graft portion against a rigid mandrel provided withinthe conduit.
 2. The system of claim 1, wherein the manifold that has gasflow passages includes a first mandrel around which the surgical conduitfits and that terminates in the internal port within the surgicalconduit, and the other manifold has a mandrel with no gas flow passages.3. The system of claim 1, wherein the valved conduit is an aortic valveconduit and the sealing ring has a peripheral shape that undulates so asto mimic the aortic annulus, and the rigid clamps each have facing clampsurfaces that undulate to match the contours of the sealing ring.
 4. Asurgical conduit leak testing system, comprising: a manifold assemblyincluding a first manifold spaced from a second manifold, each of thefirst and second manifolds sealingly clampable to a respective end of asurgical conduit, the first manifold fluidly coupling a lumen of thesurgical conduit to a testing gas port when the surgical conduit issealingly clamped thereto; a meter fluidly coupled to the testing gasport, the meter suitable for determining at least one of a gas flow rateor a gas pressure; wherein each of the first and second manifoldscomprises a piston disposed in a chamber therein, the piston isreversibly displaceable within the chamber between a first position anda second position, wherein in the first position, the respective end ofthe surgical conduit is not sealingly clamped to the respective manifoldand in the second position, the respective end of the surgical conduitis sealingly clamped to the respective manifold; and wherein at leastone of the first and second manifolds includes a mandrel, a portion ofwhich is dimensioned to receive the respective end of the surgicalconduit and an elastomeric clamping ring disposed around the portion ofthe mandrel, when the piston in the first position, the elastomericclamping ring is radially spaced from the portion of the mandrel by afirst distance, when the piston is in the second position, the pistoncompresses the elastomeric clamping ring, urging the elastomericclamping ring radially towards the portion of the mandrel to a radialspace of a second distance, and the first distance is greater than thesecond distance.
 5. The leak testing system of claim 4, wherein the gasmeter includes a mass flow meter.
 6. The leak testing system of claim 4,further comprising a pressure controller fluidly coupled to the testinggas port, the pressure controller suitable for controlling a pressure ofa testing gas.
 7. The leak testing system of claim 4, wherein one of thefirst and second manifolds includes a first end clamp and a second endclamp, the first end clamp and the second end clamp dimensioned toreceive a flange of the surgical conduit therebetween, and when thepiston is in the second position, the piston urges the first end clampand the second end clamp together to sealingly clamp the flange of thesurgical conduit to the manifold.
 8. The leak testing system of claim 4,wherein the piston is displaceable from the first position to the secondposition by applying fluid pressure thereto.
 9. The leak testing systemof claim 4, wherein at least one of the first and second manifolds ismoveable towards and away from the other of the first and secondmanifolds.
 10. A method for leak testing a surgical conduit, the methodcomprising: positioning a surgical conduit within a test fixtureincluding first and second spaced apart manifolds, each manifold havingstructure for clamping and sealing onto opposite ends of the surgicalconduit, wherein one of the manifolds has gas flow passages between anexternal fitting and an internal port that opens to an interior of thesurgical conduit when clamped thereon; wherein each of the first andsecond manifolds comprises a piston disposed in a chamber therein, thepiston is reversibly displaceable within the chamber between a firstposition and a second position, wherein in the first position, therespective end of the surgical conduit is not sealingly clamped to therespective manifold and in the second position, the respective end ofthe surgical conduit is sealingly clamped to the respective manifold;wherein at least one of the first and second manifolds includes amandrel, a portion of which is dimensioned to receive the respective endof the surgical conduit and an elastomeric clamping ring disposed aroundthe portion of the mandrel, and when the piston is in the secondposition the piston compresses the elastomeric clamping ring to sealaround the end of the surgical conduit; pressurizing a lumen of asurgical conduit with an inert gas; measuring a flow rate of the inertgas; wherein the step of pressurizing a lumen of a surgical conduit withan inert gas includes introducing the inert gas to the external fittinguntil a predetermined pressure within the conduit is reached;maintaining the internal pressure for the period of time whileperforming the step of measuring; and determining if there is a leak inthe surgical conduit based on the measured flow rate.
 11. The method ofclaim 10, further comprising sealing a first and a second end of thesurgical conduit to a test fixture, wherein the first end and the secondend of the surgical conduit are movable relative to each other.
 12. Themethod of claim 10, wherein the pressuring with the inert gas comprisespressuring with air.
 13. The method of claim 10, wherein measuring theflow rate comprises measuring a mass flow rate.
 14. The method claim 10,further comprising comparing the measured flow rate with a selected flowrate.
 15. A method for leak testing a surgical conduit, the methodcomprising: positioning a surgical conduit having a tubular graftportion within a test fixture including first and second spaced apartmanifolds, each manifold having structure for clamping and sealing ontoopposite ends of the surgical conduit, wherein one of the manifolds hasgas flow passages between an external fitting and an internal port thatopens to an interior of the surgical conduit when clamped thereon;wherein each of the first and second manifolds comprises a pistondisposed in a chamber therein, the piston is reversibly displaceablewithin the chamber between a first position and a second position,wherein in the first position, the respective end of the surgicalconduit is not sealingly clamped to the respective manifold and in thesecond position, the respective end of the surgical conduit is sealinglyclamped to the respective manifold; wherein the surgical conduitincludes a resilient sealing ring on a first end which extends radiallyoutward from the tubular graft portion, and wherein the structure forclamping and sealing on the first manifold includes a pair of rigidclamps sized and shaped to axially compress the sealing ring;pressurizing a lumen of a surgical conduit with an inert gas; measuringat least one of a flow rate or a pressure of the inert gas over a periodof time; wherein the step of pressurizing a lumen of a surgical conduitwith an inert gas includes introducing the inert gas to the externalfitting until a predetermined pressure within the conduit is reached;maintaining the internal pressure for the period of time whileperforming the step of measuring; and determining if there is a leak inthe surgical conduit based on the measured flow rate.
 16. The system ofclaim 15, wherein the surgical conduit is an aortic valve conduit andthe sealing ring has a peripheral shape that undulates so as to mimicthe aortic annulus, and the rigid clamps each have facing clamp surfacesthat undulate to match the contours of the sealing ring.